The architect has started outline designs after the practice completed a feasibility study for the redevelopment, which was published earlier this month.
The move will come as a significant positive for the theatre company after the disappointment of Erick van Egeraat's failed bid to redevelop the site, which collapsed in May last year.
Bennetts' feasibility study shows that it will be possible to retain the site's 1932 Grade II*-listed theatre - and its Art Deco interior. Egeraat had planned to demolish it.
The report argues that there is the potential to find an architectural solution within the building that will retain the historically significant elements of both the foyer and the exteriors while also producing a modern 1,000-seat auditorium.
Bennetts' feasibility study will inform the outline designs, which are expected to be submitted for planning approval in early 2006.